The present invention relates generally to an image pickup optical system comprising a prism fixing member for preventing a deterioration in the capability of correcting decentration aberration and an apparatus therefor, and more specifically to an internal reflection optical prism having image formation capabilities, to an image plane side of which a prism frame with an image pickup element such as a CCD received therein can be attached with high precision, a prism frame therefor, and an optical assembly comprising said optical prism and said prism frame.
The inventors have already filed Japanese Patent Application No. 9-172168 to come up with using a decentration optical prism comprising at least three optical surfaces, wherein light incident from an entrance surface suitable for the incidence of light from a subject is subjected to at least two internal reflections to turn back an optical path and the reflected light leaves a given exit surface to form an image of the subject, thereby picking up the subject image using an image pickup element such as a CCD located on an image plane of the prism. The inventors have also filed Japanese Patent Application No. 10-77272 to propose to construct an image formation optical system using two such decentration optical prisms, thereby picking up a subject image in the same manner as mentioned above.
To use such an image pickup system to pick up a subject image with resolution as designed and expected, it is required that the optical prism be in high-precision alignment with the image pickup element. A sensible tradeoff between high precision of alignment and easy of fabrication is now a problem awaiting solution.
In recent years, on the other hand, the fabrication of optical prisms by an injection molding process has become common. This injection molding process can cover a fairly wide range of molded articles by use of a slide mechanism.
FIGS. 33(a), 33(b) and 33(c) illustrate schematically a mold having this slide mechanism. FIG. 33(a) is illustrative of how a slider S is injected in a mold cavity C, thereby imparting the shape of the cavity C to an article being molded. FIG. 33(b) is illustrative of how the slider S is ejected from within the mold cavity C to remove out of the mold a molded article formed of plastics, etc. in the mold cavity C. FIG. 33(c) is a view showing the position relation between the slider S and the mold cavity C illustrated in FIG. 33(b), as viewed from another angle.
By use of a mold having such a slide mechanism, various forms of prisms can be molded. Such a mold is known per se, and may be applied to the molding of prisms according to the present invention.
FIGS. 34(a), 34(b) and 34(c) illustrate schematically a mechanism for moving a slider in a mold having a slider mechanism. This slide mechanism is designed in such a manner that as an angular pin AP fitted into a through-hole formed through a slider SL is displaced from within the through-hole to a given relative position, the slider SL is retracted from within a mold cavity C depending on the inclination of the angular pin AP.
FIG. 34(a) shows that the angular pin AP is fitted deep into the through-hole formed through the slider SL while a fixed mold FD is closest to a movable mold MD, so that the slider SL can be inserted into the mold cavity C to construct an intra-cavity configuration corresponding to a molded article of complicated shape.
FIG. 34(b) shows that as the fixed mold FD is relatively spaced away from the movable mold MD, the angular pin AP is pulled out of the through-hole in the slider SL, so that the slider SL is retracted from within the mold cavity C depending on the inclination of the angular pin AP, finally leaving the mold cavity C.
FIG. 34(c) shows that an ejector pin EP is ejected in the FIG. 34(b) state to remove a molded article MM having an undercut portion UC formed by the slider SL.
If an injection molding process is used with such a slide mechanism as mentioned above, it is then possible to fabricate various forms of optical prisms with relative ease yet with high efficiency.
The situations being like this, an object of the present invention is to provide an image pickup optical system comprising a prism fixing member for preventing a deterioration in the capability of correcting decentration aberration, which optical system can make a reasonable tradeoff between the precision of alignment of an internal reflection decentration optical prism having image formation capabilities, when used as an image formation element for an electronic camera, an electronic endoscope or the like, with respect to an image pickup element and ease of fabrication, and a device using such an image pickup optical system.
According to one aspect of the present invention, the above object is achieved by the provision of an image pickup optical system comprising an image formation optical system for forming an object image, and an image pickup member for receiving said object image formed by said image formation optical system, characterized in that:
said image formation optical system comprises at least one first prism member,
said first prism member comprises as optical acting surfaces at least an entrance surface on which a ray bundle strikes, a reflection surface for reflecting said ray bundle within said prism, and an exit surface through which said ray bundle leaves said prism,
said reflection surface is constructed in a curved surface form that gives power to said ray bundle, said curved surface being constructed of a rotationally asymmetric curved surface having an action on correction of decentration aberration, and
a fixing member for fixing a position relation between at least said first prism and said image pickup member is provided so as to prevent a deterioration in a capability of said rotationally asymmetric curved reflection surface of said first prism of correcting decentration aberration due to a misalignment upon setting.
According to another aspect of the present invention, there is provided an image pickup optical system comprising an image formation optical system for forming an object image, and an image pickup member for receiving said object image formed by said image formation optical system, characterized in that:
said image formation optical system comprises a plurality of optical elements including at least a first prism member,
said first prism member comprises as optical acting surfaces at least an entrance surface on which a ray bundle strikes, a reflection surface for reflecting said ray bundle within said prism, and an exit surface through which said ray bundle leaves said prism,
said reflection surface is constructed in a curved surface form that gives power to said ray bundle, said curved surface being constructed of a rotationally asymmetric curved surface having an action on correction of decentration aberration, and
a fixing member for fixing a position relation between at least said first prism and one other optical element is provided so as to prevent a deterioration in a capability of said rotationally asymmetric curved reflection surface of said first prism of correcting decentration aberration due to a misalignment upon setting.
According to yet another aspect of the present invention, there is provided an image pickup optical system comprising an image formation optical system for forming an object image, and an image pickup member for receiving said object image formed by said image formation optical system, characterized in that:
said image formation optical system comprises a plurality of optical elements including at least a first prism member,
said first prism member comprises as optical acting surfaces at least an entrance surface on which a ray bundle strikes, a reflection surface for reflecting said surface within said prism, and an exit surface through which said ray bundle leaves said prism,
said reflection surface is constructed in a curved surface form that gives power to said ray bundle, said curved surface being constructed of a rotationally asymmetric curved surface having an action on correction of decentration aberration, and
a fixing member for fixing position relations among at least said first prism, one other optical element and said image pickup member is provided so as to prevent a deterioration in a capability of said rotationally asymmetric curved reflection surface of said first prism of correcting decentration aberration due to a misalignment upon setting.
According to the present invention, it is possible to use the above protrusions and recesses or the above prism frame or image pickup element-mounting member, thereby obtaining a prism frame well fit for the optical prism, simplifying image pickup element mount work, and improving the precision of alignment.
It is here to be understood that the present invention includes a prism frame mounted to such an optical prism, combinations of such an optical prism and its prism frame with an image pickup element received therein, and an optical assembly comprising combinations of such optical prisms.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangements of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.